People Before Profit MLA Eamonn McCann said it was alarming that the gas supply to the 47 apartments at Conars Court in Londonderry had major faults.

An inspection by the Health and Safety Executive (HSE) found corroded gas installation pipework, improper ventilation, defects in the pipe shafts and a catalogue of other failures.

The complex was built as the property market crashed in 2008 and remained largely unsold and vacant until Habinteg Housing Association bought the majority of the apartments in 2014.

Shortly after tenants moved in, concerns about the gas fittings started to emerge. Many complained of headaches and nausea. After the HSE inspection in May this year the gas supply to the flats was cut off immediately - but residents have just found out the full extent of the report.

Robbie White has lived in one of the apartments for two years.

He said he was both angry and anxious at what could have befallen him and his two young sons since moving in. He said: "I asked the HSE for a copy of the report and was shocked to see that we were not just "at risk" - which is what we had originally thought - but we were in real and immediate danger.

"That is a terrifying thought when you think about how many people are living here.

"It turned out the flues could have leaked carbon monoxide due to corrosion caused by the condensed water building up in the base of them.

"On top of that, the service ducts carrying the gas piping should have been ventilated top and bottom, but this wasn't done. The result was that in the event of a leak, the escape route for the gas would have been into the communal hallways - the very place we as residents would be using as an escape route.

"The flues were not taking fumes out of the building but discharging them in the shafts inside. This raises the question of who gave Conars Court a clean bill of health in the first place, on the basis of what inspections or tests?"

Mr McCann wanted to know if other complexes exist that were passed as safe but may not be.

"In a letter last week, the Health and Safety Executive said that faulty gas pipes at the flats complex had created an "immediately dangerous" situation for residents," he said.

"We need to know how this alarming situation came about."

He added: "There needs to be a full inquiry without fear or favour into how the near disaster at Conars Court came about."

Habinteg Housing Association was not involved in construction of the building or in the installation of gas or other fittings but has assured residents it is taking the necessary action to rectify.